Configuring Your Test Point Requirements
Defining proper test points on a board layout during your design process is critical for having your PCB tested and verified by your manufacturer. This chapter will cover general testing requirements for your PCB, and will then go into the specifics of test pad placement and panelization.
General Test Point Requirements
Before going into the specifics of test point and pad requirements, there are several general guidelines to keep in mind:
- Each node on your board should have at least one test probe point.
- It is not recommended to use component leads as test points.
- It is recommended to distribute your test points throughout your board.
- The spacing between test pads (center-to-center) should be maintained at 0.100”.
Panelization also known as step-and-repeat, is the method of placing two or more PCBs onto one panel, which allows boards to be secured during manufacturing, shipping, and assembly. Panelization can also save you time by processing multiple boards at once in bulk as shown in Figure 10.
General Guidelines for Panels
Common panel sizes are 12” x 18” and 18” x 24”. The following specifications should be included for a standard panelization:
- Breakaway strips should measure around 0.400”.
- Fiducials should be at least 0.125” away from a card edge or panel frame edge.
- Panel designs should have 0.125” un-plated tooling holes located 0.2” from frame corners (or per your manufacturer's guidelines).
Finalizing Your Board Layout
By adding proper test points on a board, you will significantly increase the likelihood of detecting any manufacturing related errors during the post-production validation process. Given that every design has its limitations and unique physical constraints, it is always recommended to consult with your manufacturer to determine the ideal placement of test points.